U.S. patent application Ser. No. 13/316,164, filed Dec. 9, 2011, which is incorporated herein by reference in entirety, discloses marine engine exhaust systems that include an exhaust conduit conveying engine exhaust gas from upstream to downstream, a sensor sensing oxygen content of the exhaust gas in the conduit, and a shield located in the conduit.
U.S. Pat. No. 7,552,586, which is incorporated herein by reference in entirety, discloses a marine engine exhaust system having an oxygen sensor located within a catalyst housing structure and downstream from a catalyst device.
U.S. Pat. No. 7,467,628 discloses a control system for an oxygen sensor heater. The control system includes a passive heater control module that generates a heater control signal at a first duty cycle and measures a resistance of the oxygen sensor heater. An exhaust gas temperature mapping module maps the resistance to an exhaust gas temperature. An active heater control module generates a heater control signal at a second duty cycle based on the exhaust gas temperature.